Process for treating manganese ore



'May '21, 1957 E. B. M ANcKE PRoclass FOR TREATING' MANGANESE ORE:

Filed July 2, 1956 ATTORN Y `formed during the process.

PROCESS FOR TREATING MANGNESE ORE Edgar B. Marieke, Bethlehem, Pa., `assigner to Bethlehem `Steel Company,a corporation of Pennsylvania `Application July lZ, 1956, Serial No. 595,315

11 Claims. (Cl. 'l5- 121) v.This application is a Vcontinuation-in-part application of Serial No. 303,581, tiled August 9, 19,52, now abancloned. t i i My invention relates `tof the treatment of manganese oresfor the .purpose of separating the manganesefrom other-` constituents of the ores. It particularly relates to the treatment of the sof-called low grade manganese ores` for the purpose of obtaining products having considerably higher [contents .ofmanganese than `in the ores being treated. p l l p i, Manganese is in great demand butthere is a scarcity in the United States of manganese :bearing ores which contain `a sutiiciently high content of manganese to be profitable for treatment by the usual methods. On 'the other hand there is an abundance of so-called low grade ores containing manganese having smallercontents of manganese. My process` is particularly adapted to the treatmenttof such low grade oresV to produce products having a high manganese content whichiproducts are adapted to be treated by the usual methods employed with high grade manganese ores.` i p My invention is a process for treating manganese `ores which comprises `thesteps of Vmixing an aqueous solu- `tion of nitric acid With the ore to form a slurry, treating such slurry With nitrogen dioxide (NO2) or` nitric `oxide (NO) or amixture of nitrogen dioxide and nitric oxide, autoclaving the slurry `at av temperature of Vfrom 31.09 F. to4 650 F., separating the solution containing manganese nitrate fromvthe insoluble matter, evaporating water from the solution, and roasting the resulting .product to give manganesein `oxide form and liberate nitric acid and oxides of nitrogen. t p

Ihe accompanyingdrawing, which Iforms a part of my disclosure is a schematic ow sheet indicating the various steps of away of performing my process. Referring to the drawing, a low grade manganese ore is ground as indicated at 10. The ore is then mixed with Van aqueous solution of nitric acid and treated with NO2 `solution and insoluble portion, |and the insoluble portion washed, `as indicated at 13, the settled solids being passed oi as indicated at 13', for utilization in any detsired` way. The separated solution, containing manganese nitrate, is subjected to evaporation, as indicated at 14,'to get rid of most of therwater. The highlyconcentrated product from the evaporation stage is then roasted, as indicated at 15, to get rid of the remaining water and decompose the nitrates to form manganesev oxide and oxides of any other nitrates which have been During the roasting treatment, nitric acid is liberated as is also NO2. This nitric acid and NO2, together with Water vapor, are passed through a condenser to condense the nitric acid and water,

as indicated at 16, to form an aqueous solution of nitric aired States Parchi-O 2,793,112 Patented-May 21, `1957 p acid which` is `fed by way of pipe 17 to the mixing and treating stage of the process indicated at 11 where the nitric acid is mixed with more ore to form a slurry. During the condensation step indicated at 16, NO2 gas is separated from the nitric acid and passes by way of pipe 18 to the mixing and treating step 411 of the process. During `the stage of evaporation, indicated at 14, not only is water removed from the solution but some nitric acid is removed as Well. The vapors of Water and nitric acid from the` step of evaporation are passed through a rectier as indicated lat 19. An aqueous solution of nitric acid of the desired concentration passes from the rectier by Way of pipe 20 which joins with pipe 17 Vfor feeding the aqueous solution of nitric acid to the mixing step at 11. The Water recovered from theerectier is fed by pipe 21 to thewashing stage where the settled solids are washed.

As `an example of my process, I shall now describe the treatment of a low grade manganese ore, known `as Mangan-Louise. The particular ore of this illustration of my process contains 36% iron, 10% manganese and 0.09% phosphorus. The ore is ground to a mesh of about and then mixed with an aqueous solution of nitric acid, having a concentration of about 25%, to form a slurry. The amount of nitric acid solution used is such thatthere are present 250 parts of nitric acid and 750 parts of Water for each 1000 parts of ore being treated.

This slurry `is maintained at a temperature of about Fffor about 4 hours. During such period, NO2 gas is bubbled into the slurry. The slurry is kept agitated by anyi suitable means. The amount of NO2 gas used in this particular example of my process is about 48 parts per 1000 parts of ore being treated. During this stage of my process a considerable amount of the manganese is dissolved at a nitrate of manganese. Some of the iron of the ore is dissolved as terric nitrate and small amounts of nitrates are formed and dissolved of other ore constituents, as aluminum and calcium. A considerable amount of the phosphorus is dissolved, probably as phosphoric acid. 'Following this treatment the slurry is autoclaved at a temperature of 400 F. for 30 minutes. The pressure was about 275 pounds per sq. in. gauge. This autoclaving substantially increases the amount of manganese dissolvedas a nitrate from the ore and dissociates most of the ferrie nitrate formed in the previous stage of the treatment to precipitate iron as ferrie oxide or hydrated ferrie oxide and release nitric acid in the solution in the liquid phase. Most of the dissolved phosphorus is precipitated with the iron. The solution of nitrate of manganese and small `amounts of other nitrates is then separated from the insoluble matter, the separated insoluble portion being washed and the wash water added to the separated solution. The separated solution, carrying manganese nitrate is now evaporated to get rid of most of the Water to form a highly concentrated solution. This solution is then roasted to decompose the nitrate of manganese and other nitrates to get manganese and other metals in the oxide form, and also to liberate nitric acid and NO2 gas together with water vapor. The manganese oxide product contains most of the manganese of the ore and but little of the iron, constituting a concentrate having a high manganese to iron ratio. The liberated nitric acid and NO2 gas together with Water vapor is passed through a condenser to condense the nitric acid and Water vapor to form an aqueous solution of nitric acid and separate such acid from the NO2 gas.

The NO2 gas which is given off during the roasting stage of the process, and which is separated from the nitric acid in the condenser, is fed back to the treatment stage of the operation indicated at 11 in the drawing.

It will be apparent from the above that my process is cyclic in the sense that the reagents employed (HNOs and NO2) are regenerated and returned -for the treatment of ore in the same way as indicated above.

During the roasting treatment, some NO gas is formed in addition to the NO2, and accompanies the NO2 gas when it is fed back for the treatment ofl more ore. VThe chemical effects of the NO gas Vare similar to that of NO2 in my process.

I desire to point out the importance of the step of autoclaving at high temperatures. To show this irnportance, I shall indicate the results of treatment with and without the autoclaving step, the ore, reagents, and conditions of treatment being those of the specific example given above. The slurry of ore, involving the use of 25% nitric acid solution, was heldv at 180 F. for 4 hours While agitating and adding NO2 gas all as indicated in the speciiic example described above. Without autoclaving, the solution was separated from the insoluble matter. This solution was found to contain 3.5% of the iron in the ore, 78% of the manganese, and 46% of the phosphorus. Proceeding, as just indicated, but including the autoclaving at 400 F. for one half hour, the solution separated from the insoluble matter, contained 1% of the iron of the ore, 92.5% of the manganese and 4.5% of the phosphorus. From this it will be apparent that the autoclavingistep has considerably increased the solution ofv manganese and has considerably removed iron and phosphorus from such solution.

The importance of the autoclaving step is also shown by the diiferences in the analyses of the manganese concentrates which are produced without the autoclaving and also with it, the procedure other than the autoclaving, being identical in both cases, the ore and the conditions of operation being those indicated in the specific example given above. The analyses of the concentrates, so far as iron, manganese and phosphorus are concerned, are shown in the tables below, the analysis in Table I being that obtained when autoclaving was not employed and the analysis in Table II being that when autoclaving was used.

Table l Percent Fe 7.5 Mn 47.5 P a 0.2

Table Il Percent Fe 2.2 Mn 57.3 P 0.02

It will be obvious from these gures that a far higher grade concentrate is obtained as a result ofthe inclusion of the autoclaving step, the manganese content being considerably higher and the iron and phosphorus contents considerably lower.

In the above example of my process, certain specific conditions of operation are set forth, these conditions may be varied rather widely without departure from my essential process.

The concentration of the aqueous nitric acid solution employed may vary greatly. The concentration may vary from to 70% although I prefer a concentration of not rover 60%. The amount of acid used may vary considerably. There should be a suicient amount of acid so that the amount of nitric acid contained in the aqueous nitric acid solution plus the NO2 is at least `suiiicient to meet the stoichiometric requirements of the manganese in the ore. Preferably I use an amount in excess of these requirements. A considerable excess may be used without reducing the eiiiciency of the process.

In the example of my process given above, the slurry of aqueous nitric acid solution and ore is maintained at a temperature of 180 F. This temperature may vary considerably. In general the higher the temperature the more rapid the solvent action on the ore.

The temperature of autoclaving may vary from 310 F. to 650 F. Ordinarily, however, I vemploy a temperature from 350 F. to 450 F. When a temperature of the order of 310 F. is used, a pressure of at least 80 p. s. i. g. will be maintained in the autoclave. When the autoclaving temperature is 350 F. or higher, the pressure will be at least 135 p. s. i. g.

In the use of the term autoclaving in this invention, it is to be understood that I am referring to the wellknown process of maintaining a liquid in the liquid phase at an elevated temperature and superatmospheric pressure. For any given temperature, a definite pressure will result; this is the vapor pressure of the liquid phase. If gases are introduced, such as the NO2 gas of my invention, the pressure will be the sum of the aforementioned vapor pressure and the partial pressure of the introduced gas. Thus, within the operating temperature range of from 310 F. to 650 F., for the system herein described, a vapor pressure is maintained within the autoclave sufficient to retain the water and nitric acid in the liquid phase.

In the specic example of my process, given above, the ore is subjected to the action of nitric acid and NO2 prior to the autoclaving step. In a variation of my process the two treatments may be combined. In this form of my invention the slurry of aqueous nitric acid solution and ore is fed directly into the autoclave and there subjected to the action of NO2 gas during the autoclaving at a temperature of from 310 F. to 650 F.

My process is preferably continuous, i. e., the ore passes continuously through the mixing and autoclaving stages, and through the stage of separating the solution from the undissolved part, and the solution passes continuously through the evaporator and roasting treatments, and nitric acid solution and NO2 are continuously being fed back into the system to act on more ore. While I prefer the continuous method for manipulative and economic reasons, my process is fully effective chemically when a batch method is employed. By the batch method I mean that method of procedure wherein the receptacles in use are charged, treated and then discharged, following which another batch may be charged and treated, and so on.

My process is not only applicable to ores of manganese, but also to slags which contain this element. Where, in the claims, I refer to ore this term is to be understood as suiliciently comprehensive to include a slag.

I claim:

l. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of an oxide of the group consisting of NO, NO2 and mixtures thereof, the amount of nitric acid in the aqueous solution of nitric acid plus the oxide of nitrogen being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, autoclaving the slurry at a temperature of from 310 F. to 650 F., separating the resulting solution from the undissolved matter, removing water from the solution, roasting the manganese values from such solution and thereby producing a manganese concentrate in oxidic form high in manganese and 'low in iron.

2. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of NO2 gas, the amount of nitric acid in the aqueous solution of nitric acid plus NO2 being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, autoclaving the slurry at a tem- A perature of from 310 F. to 650 F., separating the resulting solution containing manganese nitrate from the undisarcane solved matter, removing Water from the solution, roasting the manganese nitrate from such solution, and thereby forming manganese oxide and liberating nitric acid and NO2.

3. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of NO2 gas, the amount of nitric acid contained in the aqueous nitric acid solution plus the NO2 being in excess of the amount suliicient to meet the stoichiometric requirements of the manganese in the ore, autoctlaving the slurry at a temperature of from 310 F. to 650 F., separating the resulting solution containing manganese from the insoluble matter, concentrating the solution by evaporation, roasting the concentrated solution and thereby producing manganese in the oxide form and liberating nitric acid and NO2.

4. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, autoclaving the slurry at a ternperature of from 310 F. to 650 F., subjecting the slurry to the action of NO2 gas during such autoclaving, the amount of nitric acid in the aqueous solution of nitric acid plus NO2 being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, separating the resulting solution from the insoluble matter, concentrating the solution by evaporation, roasting the concentrated solution, and thereby producing manganese in the oxide form and liberating nitric acid and NO2.

5. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of NO2 gas, the amount of nitric acid plus NO2 being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, autoclaving the slurry at a temperature of from 350 F. t0 450 F., separating the solution from the insoluble matter, concentrating the solution by evaporation, roasting the concentrated solution and thereby forming manganese in the oxide form and liberating nitric acid and NO2.

6. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of NO2 and NO gases, the amount of nitric acid in the aqueous solution of nitric acid plus NO2 and NO being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, autoclaving the slurry at a temperature of from 310 F. to 650 F., separating the resulting solution containing mauganese from the insoluble matter, concentrating the solution by evaporation, roasting the concentrated solution and thereby producing manganese in the oxide form and liberating nitric acid and NO2 and NO gases.

7. A process for treating manganese ores to produce a solution of manganese nitrate lhaving a lhigh manganese to iron ratio comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of an oxide of the group consisting of NO, NO2 and mixtures thereof, the amount of nitric acid in the aqueous solution of nitric acid plus the oxide of nitrogen being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, autoclaving the slurry at a temperature of from 350 F. to 450 F. and separating the solution from the undissolved matter.

8. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of NO2 gas, the amount of nitric acid in the aqueous solution of nitric acid plus NO2 being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, autoclaving the slurry at a temperature of from 350 F. to 450 F. and at a pressure of not less than p. s. i. g., separating the solution from the insoluble matter, concentrating the solution by evaporation, roasting the concentrated solution and thereby producing manganese in the oxide form and liberating nitric acid and N02.

9. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of an oxide of the group consisting of NO, NO2 and mixtures thereof, the amount of nitric acid in the aqueous solution of nitric acid plus the oxide of nitrogen being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, autoclaving the slurry at a temperature of from 310 F. to 650 F. and thereby maintaining a vapor pressure within the autoclave suiiicient to retain the Water and nitric acid in the liquid phase, separating the resulting solution from the undissolved matter, removing Water from the solution, roasting the manganese values from such solution and thereby producing a manganese concentrate in the oxide state high in manganese and low in iron.

l0. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of NO2 gas, the amount of nitric acid in the aqueous solution of nitric acid plus NO2 being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, autoclaving the slurry at a temperature of from 310 F. to 650 F., and thereby maintaining a vapor pressure within the autoclave sufficient to retain the Water .and nitric acid in the liquid phase, separating the resulting solution containing manganese nitrate from the undissolved matter, removing Water from the solution, roasting the manganese nitrate from such solution, and thereby forming manganese oxide and liberating nitric acid and NO2.

11. A process for treating manganese ore comprising the steps of forming a slurry of the ore and an aqueous solution of nitric acid, subjecting the slurry to the action of NO2 gas, the amount of nitric acid plus NO2 being in excess of the amount necessary to satisfy the stoichiometric requirements of the manganese in the ore, autoclaving the slurry at a temperature of from 350 F. to 450 F., and thereby maintaining a` vapor pressure within the autoclave sucient to retain the water and nitric acid in the liquid phase, separating the solution from the insoluble matter, concentrating the solution by evaporation, roasting the concentrated solution to produce manganese in the oxide form and to liberate nitric acid and NO2, and returning the nitric acid and NO2 to the treatment of more ore.

References Cited in the le of this patent UNITED STATES PATENTS 981,451 McKechnie et al. Jan. 10, 1911 1,503,229 Clark July 29, 1924 1,649,152 Clark Nov. 15, 1927 1,824,936 Travers Sept. 29, 1931 1,923,362 Frazee Aug. 22, 1933 2,005,120 Whetzel et al. June 18, 1935 2,344,004 Six Mar. 14, 1944 OTHER REFERENCES Report of Investigations 3626, March 1942. Manganese Investigations. Entire report is 30 pages and 7 gures. Published by Bureau of Mines, Washington, D. C. 

7. A PROCESS FOR TREATING MAGANESE ORES TO PRODUCE A SOLUTION OF MANGANESE NITRATE HAVING A HIGH MANGANESE TO IRON RATIO COMPRISING THE STEPS OF FORMING A SLURRY OF THE ORE AND AN AQUEOUS SOLUTION OF NITRIC ACID, SUBJECTING THE SLURRY TO THE ACTION OF AN OXIDE OF THE GROUP CONSISTING OF NO, NO2 AND MIXTURES THEREOF, THE AMOUNT OF NITRIC ACID IN THE AQUEOUS SOLUTION OF NITRIC ACID PLUS THE OXIDE OF NITROGEN BEING IN EXCESS OF THE AMOUNT NECESSARY TO SATISFY THE STOICHIOMETRIC REQUIREMENTS OF THE MANGANESE IN THE ORE, AUTOCLAVING THE SLURRY AT A TEMPERATURE OF FROM 350*F. TO 450*F. AND SEPARATING THE SOLUTION FROM THE UNDISSOLVED MATTER. 